Relations entre karstification, cadre morphostructural et incisions des vallées dans les calcaires du Dogger en Haute-Saône (plateaux de Vesoul et de Combeaufontaine)

Abstract : The Dogger Limestones of the plateaus of Vesoul and Combeaufontaine, which are located in the northern margin of the Bresse graben, are one of the most karstified areas of Haute-Saône Department. These plateaus don’t have active superficial flows. They have numerous karstic forms (sinkholes, forest hollows and closed depressions of hectometric dimensions, interrupted flows, caves, vertical shafts) in the 5 limestones formations of the Middle Jurassic (Dogger) : “Calcaires à entroques”, “Calcaires à polypiers”, “Grande Oolithe” (Bajocian), “Calcaires compacts” (Bathonian) et “Dalle nacrée” (Lower Callovian). The most numerous exokarstic forms are the multidecametric asymmetrical sinkholes, located on sections of dry valleys above the main valleys. Under the both plateaus, the subterranean waters flow in a vast networks of galleries, which could reach 9 km (Deujeau) and participate in a reorganization of drainage towards the graben of the Saône. The main part of the karst is an infra-talweg karst, which is developed in connection with the greatly fractured Dogger limestones. Its corresponds, upstreams, to the sinkholes of the consequent valleys located on the Dogger cuesta on the Northern borders of the both plateaus, under these plateaus, to the karstic active forms situated in dry valleys and to the subterranean circulations, and, on the Southern borders of these plateaus and the western border of the plateau of Vesoul to abundant emergences (Font of Champdamoy) situated in the main valleys. The subterranean galleries are oriented towards the N10° to N40° directions, in accordance with the regional faults or perpendicularly to these directions due to regressive erosion of the rivers from the Western border of the plateau of Vesoul. The infra-talweg karst also concerns high cavities, shaped in connection with valleys incision, as the cave of Equevillons (113 m) which has been shaped under conditions of drowned palaeovalleys. The forms of the lithostratigraphic karst is particularly not very numerous on the Vesoul plateau due to the low thickness of the Callovo-Oxfordian marls located on the « Dalle nacrée » formation (50 m deepth). The old age of the karstification is attested by the presence of karstic galleries until about 350 m ASL of absolute height, by the galleries lengths (10 % > 2 km), the sizes of the caves, or the presence of hectometric closed karstic depressions drained towards the endokarst. The most ancient cavities could be attributed to the beginning of the Quaternary Period, when a regional uplift occured in connection with the Jura tectonic movements and cause a general incision reaching 50 m deepth along the Saône and the lower Ognon valleys. The erosion of the ferruginous weathering profiles of the plateaus and the trapping of weathered sediments in caves (e.g. Equevillons) may be dated to this period. The intense karstification of the fractured Dogger limestones is closer to the forms of the Jura karst, rather than those of the Eastern Paris Basin, which is present at similar altitudes.
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Theses
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http://docnum.univ-lorraine.fr/prive/DDOC_T_2015_0223_HABIB_Vol1.pdf
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Submitted on : Friday, March 30, 2018 - 9:53:12 AM
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Baher Habib. Relations entre karstification, cadre morphostructural et incisions des vallées dans les calcaires du Dogger en Haute-Saône (plateaux de Vesoul et de Combeaufontaine). Géographie. Université de Lorraine, 2015. Français. ⟨NNT : 2015LORR0223⟩. ⟨tel-01754562⟩

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